I'll admit I rarely have the patience to add a lot of realism to my writing or roleplays, but my ideal exam would be a mix of both.
I love the aesthetic of a really mundane, realistic dental office. Boring waiting room, tacky colorful scrubs, cone masks, paper bibs, plastic wrap on everything, staring up at an ugly tiled ceiling, everything's just a bit outdated, and in mismatched pastels. Not a lot of explicit sadism, the dentist is probably a bit disinterested but professional, the hygienist is peppy and eager to teach me proper flossing, both a little nerdy-looking. They explain every step of what they're doing to me, and probably make small talk about the weather or my job.
As for what's being done to me, I'll be stripped nude or forced to change into a hospital gown. I'll be restrained to the chair (probably by something like this: youtube.com/watch?v=vJ5FAPe-WWw). My whole body will be palpated and examined, I'll be given a thorough genital exam in the chair, an assistant will massage or suck on my girlcock while I'm being worked on, letting me feel her braces.
I'll be subjected to painful procedures that last for hours, and I'm given a mouthful of ugly amalgam fillings. They fit me with some ridiculous headgear I can't remove, and braces with slow-release HRT or sci-fi mind control. They act like everything they're doing is completely standard procedure for a dental exam, and explain the kinky aspects with the same clinical tone they explain my cleaning and fillings.